Adjustable output voltage regulator transformer

ABSTRACT

A ferroresonant transformer having a mechanical adjustment in the limiting cross section of the core linking the secondary windings provided by a movable wedge segment in the leg on which the secondary is wound, with the longitudinal axes of movement of the segment being canted with respect to the axes of the leg so as to constitute an offset portion of the leg presenting a decreasing limiting cross section as the segment is withdrawn along its axis.

United States Patent Hart 5] Mar. 14, 1972 [S4] ADJUSTABLE OUTPUT VOLTAGE 2,646,552 7/1953 Shingledecker et al ..336/l33 REGULATOR TRANSFORMER 2,756,398 7/1956 Feinberg ..336/1 33 X l 72 Inventor: Burt E. Hart, Red Hook, N.Y. 3319204 5/1967 wear'ey 336/ 33 X [73] Assignee: lntemational Business Machines Corpora- Primary Examiner-Thomas J. Kozma tlon, Armonk, N.Y. Attorney-Hanifin and Jancin and Frederick D. Poag [22] Filed: July 30, I970 ABSTRACT [2]] Appl. No.: 59,405

A ferroresonant transformer having a mechanical ad ustment in the limiting cross section of. the core linking the secondary U.S. windings provided a movable wedge segment in the leg on [51] ll ll. Cl ..H0lf2l/06 which the secondary is wound i {he longitudimfl axes of [58] Fleld of Search 132, 133, 134 movement of the Segment being canted with respect to the axes of the leg so as to constitute an offset portion of the leg [56] References cued presenting a decreasing limiting cross section as the segment is UNITED STATES PATENTS withdrawn along its axis.

2,869,087 1/1959 Sontheimer ..336/133 X 11 Claims, 2 Drawing Figures PATENTEDHARM I972 3, 649.941

O 60 i 60 O 4o 8 U [7 2s 10 .50 52 1;21- 15 a"\.--34 c -16 mm FIG. 2

I IRON CROSS SECTION 106 1 m I 110 non 108 i \N I i I 102 l 100 i INVENTOR USEFUL OPERATINGRANGE BURT E. HART o 1 o P .04 MEAL:

ATTORNEY ADJUSTABLE OUTPUT VOLTAGE REGULATOR TRANSFORMER CROSS REFERENCE TO RELATED APPLICATION U.S. Pat. application, Ser. No. 59,406, filed on the same day as this application and assigned to the same assignee is a related application.

BACKGROUND OF THE INVENTION Field of the Invention This invention relates to voltage regulating transformers and more particularly to adjustable output ferroresonant voltage regulating transformers wherein the output voltage is alterable by a change in the saturating flux level in the magnetic path linking the output windings.

Description of the Prior Art Ferroresonant regulating transformers of the type disclosed,- for example, in U.S. Patent No. 2,143,745, issued Jan. 10, 1939, to Joseph G. Sola and entitled Constant Potential Transformer depend for their regulated output on a constant flux level in the magnetic core path linking the output winding. This constant flux level is achieved by applying a limited primary MMF to the secondarycore path while maintaining that core segment at saturation whereby the flux therein is substantially constant. Usually, this saturation is achieved by operation of a resonant circuit comprising a portion of the secondary winding in a tank circuit with a capacitor, and the limitation of primary MMF applied to the secondary core path is provided by shunting excess primary fiux across a small air gap once secondary saturation has been achieved.

In a transfonner of this kind, adjustment of the output is difficult to achieve since the magnetic path constitutes a fixed structure, the transformer is by its very nature insensitive to changes in the primary winding circuit, and the operation of the secondary circuit isdominated by the fixed saturation flux linkage of the secondary structure.

U.S. Pat. No. 3,148,326 issued Sept. 8, 1964, to O. M. Baycura et al., and entitled Ferroresonant Transformer with Saturating Control Winding addressed this problem by providing auxiliary windings for introducing a control flux and varying the effective cross section of a core section in the transformer to control the output voltage thereof.

SUMMARY OF THE INVENTION The present invention provides an infinitely variable gradation of output voltage in a ferroresonant regulating transformer by provision of a movable segment or segments in the core structure of the magnetic path linking the secondary windings. Adjustment of the position of the segment alters the limiting cross section of that flux path along a significant length of the core whereby saturation is achieved with a variable total flux. This movable segment is preferably formed with a planar side slidable along an inclined plane in the core structure, and has opposite face portion which forms a acute angle with the inclined plane. In a preferred embodiment the core structure is three legged, with the secondary core leg at its center, and the movable segments are in the form of wedges which operate along an axes which are canted with respect to the center line of that center leg in such fashion that the limiting cross section occurs within the secondary winding for minimization of leakage flux. I

Accordingly, a principal object of the present invention is to provide an improved adjustable ferroresonant regulating transformer.

Another object of the invention is to provide an improved transformer as aforesaid wherein the adjustment is by mechanical means in the core structure which is operative to reduce the limiting cross section in a portion of the core structure while maintaining an overall parallelepiped shape therein.

Still another object of the invention is to provide a mechanical adjustment in a ferroresonant voltage regulating transformer as aforesaid which provides a limiting cross section in the magnetic core over a significant core length within the secondary coil structure whereby leakage flux is minimized and accurate regulation enhanced.

Other objects of the invention will be apparent from the detailed description set forth hereinbelow and from the drawmg.

BRIEF DESCRIPTION OF DRAWING FIG. 1 is a schematic diagram of a ferroresonant transformer embodying a preferred form of the invention.

FIG. 2 is an input-output voltage diagram illustrating operation of a transformer and circuit of the kind diagramed in FIG. 1, at various operating adjustments.

DETAILED DESCRIPTION In FIG. 1 of the drawing, the illustrated ferroresonant transformer 8 comprises E and l laminations l0 and l2.-The center leg 14 mounts a primary winding 16 and one or more secondary windings 18 and 20. As is usual in ferroresonant regulators, and as indicated schematically in the drawing, one secondary winding portion can be connected to the load terminals 22, 24

and another can beconnected to a resonating capacitor 26 which imparts waveshape improvement to the output. Magnetic shunts 28 and 30 having air" gaps 32, 34 provide a return path for that portion of the primary flux which does not link the secondary windings. The gaps are air" gaps in the magnetic sense, and can be filled with fiber or the likeif desired. The portion of the primary flux which does link the 46 having a push-pull driving connection with the wedges at 48 and is threadedly engaged in transformer frame 48. The screw 46 is held in adjusted position by friction or other convenient means. Wedges 42 and 44 are urged into engagement with the sides of notch 40 by compression spring 52.

When set screw 46 is operated to move wedges 42 and 44 to a retracted position as shown in phantom line at 54, 56, the effective cross section of leg 14 is decreased from that indicated at 58 to that indicated at 60, and more of the primary flux passes through shunts 28 and 30 without linking secondary windings 18. When set screw 46 is operated to force the wedges again more deeply into slot 40, the opposite is brought about. Notch 40 extends well into the portion of leg 14 carrying secondary windings 18. As wedges 42 and 44 are forced into notch 40, they are moved together by the tapered sides of the slot 40, against the force of spring 52.

Since the adjustable portion of leg 14 is physically located within the secondary windings l8, degrading effects of flux fringing at the limiting cross section in the secondary magnetic circuit are minimized. Preferably, the range of adjustment of wedges 32 and 34 is such that, in each adjusted position, the effective cross section of leg 14 is uniform from the top to or nearby to bottom of windings 18, without affecting the cross section in the primary and shunt portions of leg 14.

Thus, notch 40 reduces the cross section of the secondary portion of leg 14 to less than that of the portion of leg 14 of the primary flux path, thus enhancing saturation of the secondary portion and improving regulation. Notch 40 need not extend all of the way from front to back of the lamination stack as shown. If additional mechanical strength is needed, the first and last few laminations can be unslotted and those E and I lamination portions can be reversed.

As illustrated in FIG. 2, a ferroresonant voltage regulating transformer of the illustrated kind provides an output voltage which rises slowly from zero as illustrated at as the input voltage rises. When the LC tank (18, 26 in FIG. 1) breaks into oscillation and the secondary core structure becomes saturated at its limiting cross section, the output voltage. rises abruptly as seen at 102 and the transformer enters a useful operating range 104 wherein further increases in input voltage applied at terminals 32, 34 yield only small increases in the output voltage at terminals 36, 38. When wedges 42, 44 are adjusted to their position all the way into slot 40 so that the limiting cross section of the secondary is as seen at 58, 58, FIG. 1, the output at terminals 22, 24 is in accordance with the maximum output line 106 in FIG. 2. When the wedges are withdrawn to the point of minimum operating position so that the limiting cross section is as indicated at 66, 60 in FIG. 1, then the output voltage operating curve is as seen at 108 in FIG. 2. An intermediate setting would yield an output as seen at 110, and so on. Accordingly, the output of the transformer can be adjusted in infinite gradations and locked into any position of adjustment by means 46 in FIG. 1. While a screw control 46 is shown, of course any suitable means including a tight fit of the parts could be utilized to maintain the wedges in adjusted position.

The three-legged E-I core configuration illustrated is of an overall shape which is often preferred in ferroresonant transformers. The angularly sliding segment arrangement of the invention is particularly useful in such a structure, where the desirable location for adjustment, the center leg, is rather inaccessible. However, the principles of the invention would have utility in other core configurations as well. Thus, a single inclined wedge of the invention could be utilized in the side of the secondary winding bearing leg of a U-l core. Such a configuration would be similar to one half of the symmetrical arrangement shown.

Thus, while only one embodiment of the present invention has been illustrated in detail it will be understood that the invention may take other forms within the spirit of the invention and the scope of the appended claims. What is claimed is:

1. In a ferroresonant transformer, a magnetic core structure comprising primary flux means and secondary flux means,

primary winding means linking said primary flux means and secondary winding means including resonating winding means linking said secondary flux means,

the improvement comprising mechanical adjustment means in the magnetic core structure of said secondary flux means adjusting substantially the limiting cross-section of magnetic material in the path of said secondary flux means linking said secondary winding means,

whereby the total saturation flux in a flux limiting portion of magnetic material in said secondary flux means is adjustable,

said adjustment means comprising a first surface on said core structure inclined with respect to the flux direction therein, and a relatively moveable core segment having a mating surface slideable obliquely of said flux direction along said first surface,

a limiting cross-section of said secondary flux means being formed cooperatively by the portion of said core structure having said first surface and by adjacent portions of said moveable segment,

said limiting cross-section, upon its saturation, altering by its adjustment, the flux amplitude of the flux-magneto motive operating curve of said secondary flux means without essential change in the shape of said curve.

2. A transformer in accordance with claim 1, wherein said segment comprises a wedge-shaped mass bounded by said mating surface and an outer surface disposed parallel to said flux direction.

3. A transformer in accordance with claim 2, wherein said core structure and said segment together form a section of said secondary flux means which constitutes a variable parallelepiped which changes in cross-section but not essentially in shape as said segment is moved along said first surface.

4. A transformer in accordance with claim 3 wherein said core structure has a second inclined surface disposed with respect to said first surface to form a V slot in said core structure aligned in said flux direction,

and wherein said adjustment means includes a second wedge shaped mass constituting a core segment slideably engaging said second surface.

5. A transfonner in accordance with claim wherein said adjustment means is symmetrical.

6. A transformer in accordance with claim 5 wherein said adjustment means includes a means acting between the first and second segments urging them against said first and second surfaces.

7. A transformer in accordance with claim 6 wherein said last mentioned means is a compression spring.

8. A transformer in accordance with claim 7 wherein said adjustment means includes means to move said segments simultaneously along said first and second surfaces.

9. A transformer in accordance with claim 8 including means for locking said segments in adjusted positions.

10. A transformer in accordance with claim 9, wherein said core structure is symmetrical about said adjustment means.

11. A transformer in accordance with claim 1, wherein said limiting cross-section is located within said secondary winding means. 

1. In a ferroresonant transformer, a magnetic core structure comprising primary flux means and secondary flux means, primary winding means linking said primary flux means and secondary winding means including resonating winding means linking said secondary flux means, the improvement comprising mechanical adjustment means in the magnetic core structure of said secondary flux means adjusting substantially the limiting cross-section of magnetic material in the path of said secondary flux means linking said secondary winding means, whereby the total saturation flux in a flux limiting portion of magnetic material in said secondary flux means is adjustable, said adjustment means comprising a first surface on said core structure inclined with respect to the flux direction therein, and a relatively moveable core segment having a mating surface slideable obliquely of said flux direction along said first surface, a limiting cross-section of said secondaRy flux means being formed cooperatively by the portion of said core structure having said first surface and by adjacent portions of said moveable segment, said limiting cross-section, upon its saturation, altering by its adjustment, the flux amplitude of the flux-magneto motive operating curve of said secondary flux means without essential change in the shape of said curve.
 2. A transformer in accordance with claim 1, wherein said segment comprises a wedge-shaped mass bounded by said mating surface and an outer surface disposed parallel to said flux direction.
 3. A transformer in accordance with claim 2, wherein said core structure and said segment together form a section of said secondary flux means which constitutes a variable parallelepiped which changes in cross-section but not essentially in shape as said segment is moved along said first surface.
 4. A transformer in accordance with claim 3 wherein said core structure has a second inclined surface disposed with respect to said first surface to form a V slot in said core structure aligned in said flux direction, and wherein said adjustment means includes a second wedge shaped mass constituting a core segment slideably engaging said second surface.
 5. A transformer in accordance with claim 4 wherein said adjustment means is symmetrical.
 6. A transformer in accordance with claim 5 wherein said adjustment means includes a means acting between the first and second segments urging them against said first and second surfaces.
 7. A transformer in accordance with claim 6 wherein said last mentioned means is a compression spring.
 8. A transformer in accordance with claim 7 wherein said adjustment means includes means to move said segments simultaneously along said first and second surfaces.
 9. A transformer in accordance with claim 8 including means for locking said segments in adjusted positions.
 10. A transformer in accordance with claim 9, wherein said core structure is symmetrical about said adjustment means.
 11. A transformer in accordance with claim 1, wherein said limiting cross-section is located within said secondary winding means. 